Safety electric coupler



Feb. 14, 1928.

L. A.. BROWN SAFETY ELECTRIC COUPLER Filed Jan. 5.- 1926 Inventor.-

Patented F eb. 14, 1928.

UNrrrn STATES PATENT ori-*lc SAFETY ELECTRIC COUPLER.

Application led January 5, 1926. Serial No. 79,363.

This invention relates to electric couplersA or connectors and, while not limited thereto, Ais especially adapted for connecting shot firing cables used in mines to a magneto, .bat-

tery or other source of current. l

The principal object of the present invention is to provide a coupler of this class which will normally short circuit the shot.

'firing cable thereby preventing'stray currents of electricity traveling throughi said cable from causing premature firing of the shot.

Another obj-ect is to provide a coupler which will facilitate the connecting and disconnecting of a cable to a source of power. It is mow the practice in firing shots in 4a mine, for the shot tirer to lay his cable, which is 100. feet orso in length,.along the mine` entry where thel shot is located. He'

lQ0 then attaches the cable to the shot and goes back'to the other end of the cable and attaches-*the cable toV a magneto or battery,

either of which maybe used to supply the electric current for firing the shot. If'a ma cto is used it is set in motion after the cab e is attached to generate current to tire the shot, while if a battery. is used a switch is Voperated to .complete the circuit through the cable. ,t

,After the shot is fired, the shot ltirer disconnects the cable from the source lor" electriccur'rent and then roceeds to connect the other end to a new s ot. y

When the cable is laid on the mine floor while it is being connected to the shots, it is parts of the cable on which the' insulation has been broken, to come into contact with ground,- track rails, or pipe lines and thereby pick up stray currents from the trolleysystem or other source and thereby cause a premature explosion of the shot.

By the use 'of the present coupler any danger of a premature explosion from the above r causes is entirely eliminated, since the coupler short. circuits the wires of the cable and forms.. a path for any stray currents picked up which is of less resistance than the spark gap path through the shot.

In-the Figure 1 islal side elevation, partly in section, showing my improved coupler connecting amshot firing cable to a magneto.

possible for the ends of the cable, or other Figure 2 is a plan view of the same also partly in section.

vFigure 3 is al sectional View through the Contact Afinger and plug. .l Referring more particularly to the drawings, the letter A designates a shot firing ca ble which is composed of two insulated wires 2'and 3 twisted together and provided at one end with universal connector clips 4 und 5 for connection with the wireleads ex* tending outwardly through the coal face ironia shot., The other ends of the wires 2 and 3 of cable A are secured to screw posts (iV and 7 which are in electrical'contact with spring contact fingers 8 and 9, respectively,v of the coupler B.

The coupler B comprises a receivin Iporn tion or jack composed of a tubular insu ating caslng or housing 10 having its rear end in# ternally threaded to receive a'threaded end 'piece or block 11 which forms a supportfor the spring lcontact fingers 8 and 9. The

fingers 8 andl 9 are secured in place by screws 12 and 13 :and the screw posts 6 and 7, respectively.

The forward end ofthe casing 10 is closed by a walllft which is provided with a centrally arranged port or opening 14 for the reception of a contact plug composed of a body portion 15 of insulating material and a pair of contact strips or plates 16 and 17 mounted on opposite sides of said bod portion so as' to be insulated from each ot er.

The strips or plates 16 and 17 extend rearwardly beyond the body portion 15 of the plu and are hingedly secured to a pair of bin ing arms 18 and 19 adapted to be secured to the Abndin post of the magneto C, which is of standard construction. If a shot ring battery is used instead of a magneto as a sourceof current the arms 18 and 19 would be secured to the'binding' posts .on the" battery switch: orkey.

The strips or plates l6and' 17 are adapted.' to contact with the fingers 8 and 9 to form an electrical connection between the source of current and the cable.' yThe strips 16 and 17 are provided with recesses 20 and 21 adapted to receive projections 22 and23 of the fingers which are normally inr contact with eachl other thereby short cireuiting the lfingers 8 and 9, and which are separated so as to break -the-short--eircuit when thecontact plug isforcedvbe'tween.theiingersand 9.

i In operation the receiving portion or jack 'of the ,coupler is. separated from the plug...

and secured to th'cc'able while the plug -portion is secured to the source of current Supply..y ff When the receiving 'portionor Jack of the I coupler is separated from the plug the contactzbuttons 124 and 25 will l' be forced into ContactI by the spring fingers 8 and 9, thereby formlngla short circuit of the cable wires "through the fingers 8 and 9 and the buttonsv 24 and 25.

f Since'the ends of the cable are enclosed within the insulating casmg l0 it is impossiy ble forthem-to'piek up any stray currents,

and if any breaks in the cable insulation Vshould permitstray currents to enter the cable, Such curr y nts/would floW through the fingers 8 and 9 and Contact buttons 24 and 25 back to ground as the path, of least resistance instead of through the spark gap at the-shot, thereby-fentirely eliminating the possibility o fa/ premature explosion from this cause.

While I have shown anddescribed one r specific embodiment of my invention, it will be understood that Ido not wish to be limited thereto 'since various modifications in details may be made without departing from the so'opcY of'my invention'as defined in the appended claim.

Iolailn: 1-

- Ina safety coupler for connecting shot firing cables 4to a source of electric current, a

`socket membercomprising a-tubular casing composed wholly of insulating material, plugs closing. the ends of said casing and also composed wholly of insulating material, one of said end plugs being provided with a centrally arranged integral post portion, a pair of spring contact fingers secured to and supported on the opposite ,sides of said post portion`otl said plug and extending inwardly within said casing in parallel and spaced relation, the other' of lsaid end plugs being apcrtured to permit the entrance of a connecting plug adapted to connect with said contact fingers, said fingers being reversely bent adjacent their forward ends to form relatively' sharp knife-like inwardly projecting contact edges'adapted to contact with the connecting plug, saidrst named end plug being apertured at space'd points to permit the entrance of the separate wires of a shot tiring cable, said Wiresbeing Secured' 

